Years ago I did the Pocket-WiFi for Japan and Korea and it was worth it because all the US carrier back then don't have an affordable international data option. I think the Pocket-WiFi rental back then was like $8 to $10 a day for unlimited data, and carriers was charging a pay per use per Kilo-byte rate.
But now almost every carrier got either cheap or free international data option, I really don't know if you want to carry another device with your just to use the internet. Also you will have to keep it charge too.